In the prior art, filter connectors typically have a filter element disposed upon a portion of the connector contact. Such a filter element may comprise a pi section filter which includes inductive and capacitive components for the purpose of attenuating unwanted signals, such as radio frequency interference.
A filter connector of the aforementioned type is disclosed in U.S. Pat. No. 4,029,386 granted to Krantz et al. In the filter connector of the Krantz patent, each of the contacts is provided with a filter element in the form of a cylindrical sleeve disposed over the center conductor of the contact in a region between the mating end of the contact and the wire receiving end of the contact. The filter network may include one or more capacitors having a common ground electrode disposed on the exterior surface of the sleeve. The ground electrode is connected to the shell of the connector member which constitutes circuit ground, through a circular ground plate within the shell. The ground plate is provided with an opening for each contact of the connector and each opening has plural spring fingers in frictional engagement with the ground electrode on the respective filter element. The ground plate is connected with the metal shell of the connector through a conductive ring having multiple spring fingers thereon. Such a ground plate with spring contacts is advantageous in that it provides a solderless ground connection.
In certain applications, it is desirable to utilize filter connectors wherein one or more contacts are provided with a compound filter i.e. a filter made up of two or more filter elements. For example, such a compound filter may comprise a pair of pi filter sections in cascade wherein each pi section is a physically discrete element. Also such a compound filter may comprise an unbalanced pi filter wherein a pi section and a shunt capacitor section are connected in cascade, each comprising a physically discrete filter element.
In filter connectors with compound filters, one of the problems in the prior art is that of providing a suitable ground connection for the filter element. In one arrangement, with the filter elements connected end-to-end, a common ground connection may be provided for connecting the ground electrodes of the filter capacitor to the connector shell. One difficulty found in this arrangement is that the adjacent active electrodes of the capacitors in the two filter elements are subject to flash-over resulting in failure of the filter.
Prior patents which relate to ground connections, especially ground plates having spring contacts, include U.S. Pat. No. 3,710,285 to Schor, et al., U.S. Pat. No. 3,569,915 to Sorenson, et al., U.S. Pat. No. 3,721,869 to Paoli, and U.S. Pat. No. 3,825,874 to Peverill.
A general object of this invention is to provide an improved capacitor electrode and grounding arrangement for filter connectors having compound filters.